This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction and Rationale A major goal of my laboratory has been to understand the fundamental mechanisms by which a large body of genes is directed to be either expressed or repressed in a cell-type or stage-specific manner or in response to signals from outside. In this context, we identified a nuclear architectural protein, SATB1, which functions as a global gene regulator, expressed in embryonic stem (ES) cells and adult progenitor cells, such as thymocytes. Using a DNA affinity column containing BUR (base unpairing region) specifically recognized by SATB1, we wish to identify SATB1 associated proteins as well as new BUR-binding proteins in stem cells and adult progenitor cells. Furthermore, we wish to test a hypothesis that the SATB1 protein undergoes changes in post-translational modification during differentiation or upon irradiation. The goal of the project is to assign specific functions to each type of post-translational modification of the SATB1 protein, similar to the concept of the 'histone code'.